Frequency-dependent inbreeding depression in Amsinckia.

Area of Science:

• Evolutionary Biology
• Plant Sciences
• Ecology

Background:

• Inbreeding depression, the reduced fitness of offspring from self-pollination, can be influenced by environmental factors.
• The competitive environment, specifically the frequency of selfed versus outcrossed individuals, may impact inbreeding depression magnitude.

Purpose of the Study:

• To investigate if inbreeding depression is affected by the frequency of inbred plants in a plant's competitive neighborhood.
• To examine the influence of neighborhood composition on the fitness of selfed and outcrossed progeny in two Amsinckia species.

Main Methods:

• Competition experiments were conducted using artificial stands with varying mixtures of inbred and outbred progeny from two Amsinckia species (A. gloriosa and A. douglasiana).
• Fitness of target plants was assessed in relation to the frequency of inbred neighbors in the artificial stands.

Main Results:

• The fitness of progeny was significantly influenced by the composition of the competing neighborhood.
• For Amsinckia gloriosa (a near-complete selfer), maximum fitness occurred at intermediate frequencies of inbred neighbors.
• For Amsinckia douglasiana (a partial outcrosser), the pattern of fitness response to inbred neighbors was opposite to that of A. gloriosa.

Conclusions:

• Competition among progeny can play a role in the selection for self-fertilization.
• These findings suggest that ecological interactions, such as competition, may contribute to the maintenance of mixed mating systems in plants.